1. Field of the Invention
This invention relates to additives which improve the compressive strength and workability of cementitious composition such as cement, cement slurries, mortar, grout and concrete.
2. Description of the Prior Art
Concrete is a hard, strong building material made by mixing cement, sand, gravel and water. Water in the mixture causes the cement to set and bind the entire mixture in a hard mass. It is well known in concrete technology that the strength--usually the compressive strength as measured by the ASTM test C39-72--is a reliable criterion of general quality. For this reason, the whole technology of concrete is developed around obtaining a significant and practical strength with a minimum of cost, and a maximum of convenience in use. Despite extensive research, most of the concrete presently being used are simple mixtures of sand and coarse stone containing a minor proportion of portland cement with sufficient water being added to produce a mixture fluid enough to place in forms.
It is well known in the art that reducing water in concrete increases the compressive strength and other properties as well. Considerable research has been directed to discovering mixtures of different particle sizes of sand and stone which will give fluid concrete having minimum water content. Also, various organic and inorganic additives have been found which permit reduction in the water content of concrete. One such additive, the sodium salt of naphthalene sulfonic acid formaldehyde condensate is used commercially for this purpose. This additive also increases the strength of hardened concrete. See U.S. Pat. No. 2,141,569--Tucker--Dec. 27, 1938.
Further, U.S. Pat. No. 3,537,869--Proell--Nov. 3, 1970 describes use of additives containing sulfonated condensation products of formaldehyde and naphthalene or salts thereof in combination with lecithin, partial fatty acid esters of polyols, their ethoxylates, sulfates, etc., in concrete mixes to increase compressive strength of the hardened concrete.
Additionally, use of hydroxy aromatic materials in cement and concrete is shown below.
CA 71 104857s discloses effect of pyrocatechol, pyrogallol and condensed and hydrolyzed tannins as accelerators for cement with various results upon acceleration and mechanical strength.
CA 88 125395f discloses effect of gallic acid plus triethanolamine in cement production upon moisture content of the clinker.
CA 88 138827y discloses effect of monocarboxylic aromatic hydroxy acids in retarding hardening of slurries of portland cement.
CA 92 151993b describes effect of tannic acid on the setting of portland cement.
CA 71 84287a discloses effect of chestnut tannin as a retarder in cement.
CA 58 9946a discloses effect of resorcinol and hydroquinone in the rate of hardening of cement.
British Pat. No. 354,502 describes addition of tannin and tannic acid to cement clinker.
CA 75 39979z discloses effect of salicylic acid on workability and setting times for mortar and concrete.
U.S. Pat. No. 188,679--Schaffer--Mar. 20, 1877 discloses use of salicylic acid in the manufacture of artificial stone from portland cement, sand and crushed stone.